Motor control system



Jan. 17, 1939. E, w|LBER 2,144,445

MOTOR CONTROL SYS TEM Original Filed Sept. 18, 1936 "(I'IIF .96" I o I V4 INVENTOR Y A TTORNE Y6.

Patented Jan. 17, 1939 UNITED STATES PATENT OFFICE MOTOR CONTROL SYSTEMcorporation of application September 19, 1936, Serial Divided and thisapplication March 4, 1937, Serial No. 128,915

4Claims.

an improved battery charging and distribution system of the type inwhich a generator associated with the system is driven by an internalcombustion engine, and in which the output of the generator may be usedto charge a battery and also to supply additional distribution circuits;to provide such a system in which for starting purposes, the battery maybe rendered effective to drive the generator as a motor to crank aninternal combustion engine; to provide such a system in which thegenerator, the internal combustion engine, and the various controlapparatus associated therewith may be embodied in a relativelyself-contained unit, which may be economically manufactured, assembled,and maintained.

Other objects of the present invention are to provide a system of theabove generally stated character, embodying improved means forautomatically stopping the driving engine in the event the battery to becharged thereby is fully charged and no power is being used in thedistribution circuit; to provide such a system in which the stoppingmeans is ineffective so long as current is being used in thedistribution circuit; to provide such a system in which the stoppingmeans embodies a relay mechanism responsive to the generator voltage,the actual voltage drop across such mechanism being further controlledin accordance with current conditions in the battery; and to providesuch a system in which the stopping relay mechanisms act to inten'uptthe engine ignition circuit.

with the above and other objects, as well as more specific objects, inview, preferred but illustrative embodiments of the presentdnvention areshown in the accompanying drawing, throughout which correspondingreference characters are used to designate corresponding parts, and inwhich;

Flgue 1 is a view in elevation, partly in section, of a combined engineand generator unit; and

Figure2 is a schematic control diagram showing the improved automaticshut-down mechanism of the present invention.

Referring first to Fig. 1, a preferred engine and generator unitcomprises generally the internal combustion engine, designated as awhole as 20, and the direct current generator, designated as a whole as22, although it is to be understood that the improvements of the presentinvention may be associated with generating systems of other types, theengine 20 may be of generally conventional construction, and asillustrated is of the single cylinder type. The piston 24 isverticallyreciprocable, and the connecting rod 26 associated therewith isconventionally connected to the offset 28 associated with the crankshaft 30. The crank case housing 32 is formed to provide one bearing 34for the crank shaft 3|], and a second bearing 36 therefor is provided bythe end bell 38 associated with the generator 22. The bearing 36 isillustrated as comprising ball bearing elements 40 and the bearing 34may, if desired, be correspondingly arranged. A suitable packing gland,

such as 42, is provided to prevent the; escape of lubricant from thecrank case along the shaft 30.

A conventional flywheel 44 is keyed to the shaft 30', externally of thecrank case 32. The yoke 48 of the generator, of conventionallycylindrical construction, supports four poles 49 in radially spacedrelation to the armature 41. Yoke 48 is closed at one end by the cover48 and is closed at the other end by the previously mentioned end- Dell38. The generator brush assembly designated generally as 50, is suitablysecured in circumferentially adjustable relation to web 53 secured tothe one end of the yoke 46 and within the end bell 38. The supply tank54, for the engine 20, is directly supported by the yoke 46, in aposition conveniently adjacent the engine 20.

It is contemplated that in practice ventilating features will be used inconnection with the gen-' erator 22, but these features form no part ofthe present invention and in order to si p ify the drawing have not beenillustrated. Preferably, and as illustrated, the right hand end of thecrank shaft 30, as viewed in Fig. 1, is provided with a drive pulley 52,through which engine 20 may drive further apparatus (not shown) inaddition to generator 22, and which pulley may be used for emergencycranking service.

Referring particularly to Figure 2, the previously mentioned generator22 is arranger; to supply charging current to the storage battery 88 andto a. plurality of distribution circuits which include, in the presentinstance, load elements represented by electric lamps I0 and I2. Thebattery is illustrated as permanently connected across the generator, inseries with a conventional cutout 82. The distribution circuits arearranged for individual control by conventional switches 84 and 86.

' The cut-out 82 is illustrated as including the 'usual current coil82a, voltage coil 82!), and contacts 820 in series with the currentcoil. The voltage coil is connected to ground and so is con necteddirectly across the armature of the generator 22. The series coil 82a,on the other hand, is energized only following closure of the contacts820. The contacts 820 are normally maintained open by the spring 82d.

The shut-down feature of the present invention is provided by the relay96, the coil of which is illustrated as connected across the armature ofgenerator 22 in series with the generator regulating series fieldwinding 22a, and the contact 96a of which is shown as connected into theignition circuit of the generator driving engine 20. The

contact 96a of relay 96 is normally closed and the relay is so designedas to open this contact only when the voltage across the winding 96somewhat exceeds the voltage corresponding to the fully chargedcondition of the battery 66. y

In the operation of the present system, it is preferred to use agenerator which has a substantially uniform voltage characteristic, sothat under all load conditions, the voltage supply by the generatortothe battery and distribution circuits is of uniform value. In instancessuch as the present one, in which the generator 22 is driven by aninternal combustion engine, it may be expected that the speed of theengine will vary between reasonable limits in response to varying loads.In such instances, accordingly, it is necessary'that the generator be soconstructed and arranged as to maintain its voltage substantiallyconstant, not only in response to varying loads, but in response tovarying speeds. A preferred construction of generator having thesecharacteristics is described in detail and claimed in applicants aboveidentified parent application, although other generator constructionsmay be used in the practice of the present invention- The system may beplaced in operation by closing the manually operable. starting switch80, which action connects generator 22 to the battery 68 in series withan auxiliary or starting series field winding 66 provided on thegenerator 22. The battery 68, which is to be charged by the system whenthe latter is in operation, thus acts to supply power to generator 22,causing it to operate as a motor and crank for the engine 20. The justmentioned starting circuit for the generator 22 extends from oneterminal of the battery 68 through the field winding 66, the armature ofgenerator 22 and shunt field winding 62 to the other terminal of thebattery. Windings 66 and 62 are cumulative under these'conditions, andact to supply a strong field to the machine 22 causing it to develop asufficiently high torque to crank the engine 20. Closure of the switch80 also completes the ignition circuit for the engine 20, which circuit.extends from the positive terminal of the battery through'the winding6'6, switch 80, generator regulating series field winding 64, normallyclosed contact 96a, breaker 92, and the primary 94 of the ignition coilto the negative terminal of the battery. As soon as the cranking actioncauses the engine 20 to drive itself, it assumes an operating speed inexcess of the speed at which battery 68 is effective to operate battery22 as a motor and thereafter the engine 20 drivesmachine 22 as agenerator. As soon as this relation is obtained, the starting switch 80may be opened, excluding the starting winding 66 fromthe circuit.

During the time that the battery 68 is driving relatively low value.

generator 22 as a motor, the voltage coil 82!) of the cut-out 82 issubjected to a voltage proportional to the terminal voltage of themotor. The voltage across coil 8212 does not become sufficient to closethe contacts 820, however, until such a time as the engine 20 starts inoperation and drives machine 22 as .a generator. As soon as this occurs,the output of generator 22 assumes a value sufiicient to cause coil 82bto close the contacts 82d, thus connecting battery ,,68 across thegenerator 22 through the cut-out 82. It will be appreciated that thewinding relation between the coils 82a and 82b is such that these coilsare cumulative so long as the generator supplies current to the battery,and so cooperate to hold the contacts 820 closed. If for any reason thevoltage of the generator should fall below that of the battery, so as tocreate a tendency for the battery to supply current to the generator,the coils 82a and 82b become subtractive, and cause the contacts 620 topromptly open.

Closure of the cut-out 82, in addition to rendering the generator 22efiective to supply charging current to the battery 68, also renders iteflective to supply current to any of the distribution circuits whichmay be closed by operation of the associated manual switches 84 and 86.At the same time, generator 22 also impresses apredetermined voltageacross the winding 96 tending to cause the contacts thereof to open.

It will be noted the coil 96 is included in one of a plurality ofparallel branches of a circuit which includes as a series element theregulating series field 64. The voltage drops across the three branchcircuits, including respectively the battery 69 and lamps i6 and 12, areof course always equal, and these voltage drops, plus the voltage dropacross the series coil 62a of the cut-out 82, are always equal to thevoltage drop across the relay coil 96. The balance of the externalgenerated voltage of generator 22 is consumed as a voltage drop acrossthe series regulating winding '64. The drop across each branch circuitand the drop across winding 64 thus depends upon the effectiveresistance of each branch circuit and the number of such branch circuitswhich are closed. Where, for example both distribution circuits areclosed, and battery 68 is in a relatively discharged state, the dropacross relay 96. is of a If one or both of the distributions are opened,the resultant increase in total resistance of the load circuit isreflected as an increase in the voltage across the relay 96. The maximumvoltage drop across relay 96 is produced when the battery reaches afully charged condition and both distribution circuits are open. At thismaximum voltage relay 96 operates to open the contacts 96a and interruptthe driving engine ignition circuit, thereby stopping the system. Relay96 may be conventionally constructed to retain its contacts when openedin open position until the generator'voltage has fallen to a valuecorresponding to such a low speed of the engine that a crankingoperation is necessary torestart the engine. Preferably, relay 96 isconstructed to have a slow release, so that it retains its contacts openuntil the engine has come entirely to rest.

This maximum oroperating voltage of relay 96 is not obtained, however,if either or both of the distribution circuits are closed, eventhough-the battery 68b is in the iu1ly'chargedcondition,

reduces the total resistance of the generator load field winding 84 anddecreases the voltage drop across the winding 96.

Following each starting operation of the system, accordingly, the engineremains in operation as long as any distribution circuit is closed andas long as the voltage of the battery 88 is below the voltagecorresponding to a fully charged condition thereof. The stopping of thesystem on the other hand occurs automatically when the battery reaches afully charged condition provided no distribution circuits are closed. Ifat the time the battery reaches the fully charged condition one or moredistribution circuits are closed, the engine remains in operation untilall distribution circuits are opened, at which time the engine isstopped.

Although a specific embodiment of the invention has been shown anddescribed, it will be appreciated that various modifications in theform, number and arrangement of parts may be made within the spirit andscope thereof.

What is claimed is:

1. In a system of the character described, a generator, a battery to becharged by said generator, an openable and closeable distributioncircuit to be supplied by said generator; means having predeterminedresistance; means connecting said battery, distribution circuit andresistance means to said generator with said battery and saiddistribution circuit in parallel branches of a circuit which includessaid resistance means in series; relay mechanism connected in parallelwith said battery circuit branch and in series with said resistancemeans; said relay mechanism and said resistance means being soproportioned relative to said battery and distribution circuits thatsaid relay is-prevented from receiving sufiicient voltage to operatesaid relay except when said distribution circuit is open and saidbattery is in a fully charged condition; and means actuated by saidrelay mechanism for controlling said generator.

2. An electrical system of the character described comprising agenerator having a regulating series field winding; a battery to becharged by said generator; a distributioncircuit selectively openableand closeable and adapted to be supplied by said generator; circuitconnections for connecting said battery and said distribution circuit inparallel with each other and to said generator in series with saidregulating series field s winding; relay mechanism connected in parallelto said battery circuit branch and in series with said regulating seriesfield winding; said relay mechanism and said field being so proportionedrelative to said battery and distribution circuits that said relay isprevented from receiving sufficient voltage to operate said relay exceptwhen said distribution circuit is open and said battery is in a fullycharged condition; and means actuated by said relay mechanism forcontrolling said generator.

3. In a system of the character described, utilizing a generator; 8.drive member for said generator; a battery to be charged by saidgenerator; and an openable and closeable distribution circuit to besupplied by said generator; the combination in said system of meanshaving predetermined resistance; means connecting said battery,distribution circuit, and resistance means to said generator with saidbattery and said distribution circuit in parallel branches of a circuitwhich includes said resistance means in series; relay mechanismconnected in parallel with said battery circuit branch and in serieswith I said resistance means; said relay mechanism and said resistancemeans being so proportioned relative to said battery and distributioncircuits that said relay is prevented from receiving sufficient voltageto operate said relay except when said distribution circuit is open andsaid battery is in a fully charged condition; and means renseries withsaid regulating series field winding;

relay mechanism connected in parallel .to said battery circuit branchand in .series with said regulating series field winding; said relaymechanism and said field being so proportioned relative to said batteryand distribution circuits that said relay is prevented from receivingsufllcient voltage to operate said relay except when said distributioncircuit is open and said battery is in a fully charged condition; andmeans rendering said relay mechanism efiective to control said drivemember,

HARQLD E;

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